Systems for treating a part of a body, for example by cutting hair on a part of a body to be treated (such as a human or animal body), include powered hand-held devices, for example trimmers, that are placed against a part of a user's or subject's body and moved over areas where hair is to be cut. Such systems include mechanical hair cutting devices. The user of the system typically selects a cutting length by adjusting or selecting a guide, such as a comb or guard, which extends over a cutting blade and then selects which areas of hair to cut and which areas should not be cut by positioning and moving the device appropriately.
When cutting a user's own hair, or someone else's hair, significant skill is required to create a particular hairstyle or to provide a presentable result. Therefore efforts are being made to provide systems that are able to automatically cut hair and create a particular hairstyle. Some types of devices are held by the subject or user during use and the hair cutting length is adjusted automatically according to the position of the device on the part of the body. Thus, these types of devices require some means to enable the device to determine its position on the part of the body.
WO 2013/096572 describes one such automated hair cutting system in which a positioning structure is placed on a user and a hair cutting device interacts with the positioning structure to determine a position of the hair cutting device relative to a reference point.